Influence of marine sources on PM10 levels and composition in the northern coast of France
Résumé
The Nord-Pas-de-Calais region is one of the most concerned areas in France by exceeding of the PM10 daily mean limit value (50 μg/m3). For a better understanding of these phenomena, the most complete identification of PM10 is crucial. In this region, numerous studies aiming to the characterization and identification of particles in urban area and in the vicinity of industrial emission have been performed. Nevertheless, the particulate atmospheric background level could also be high in coastline sites without any direct impact of urban and industrial sources. On the one hand, the influence of long range transport and gas to particle conversion should not be neglected. On the other hand, there is still a lack about the impact of emissions resulting from the marine compartment including natural emissions such as sea salts (Manders et al, 2010) and anthropogenic emissions linked to the marine traffic especially in the English Channel, together with the Straits of Dover, that forms a narrow corridor with one of the greatest concentration of shipping in the world (EEA, 2013) (700 to 800 vessels sailing per day). In this work, an intense PM10 sampling and measurement campaign has been done continuously from 2013/01/01 to 2014/04/15 at the Cape Gris-Nez (CGN), a coastal French site selected to study marine impact, in front of the Straits of Dover. A complementary campaign has been performed in the port of Calais, from 2014/01/28 to 2014/04/21. PM10 levels were measured using MP101 analyzer and collected using Digitel® DA80 sampler (30m3/h, 24h, Pall® QAT-UP filter). The characterization of PM10 was performed considering trace metals, water soluble ions, EC/OC, biomass burning and biogenic particles organic tracers. These chemical parameters were considered to explain PM10 levels observed in the Nord-Pas-de-Calais region and to estimate the contribution of the maritime sector to the PM10 levels in coastal sites. In 2013, at Cape Gris-Nez, PM10 mean value was 22.8 μg/m3 and in the same level as those observed in several other sites in the Nord-Pas-de-Calais region. 11 days exceeding the daily limit value were recorded, mainly associated with East winds typically encountered during anticyclonic conditions. The air-mass back-trajectories study evidences that the collected particles in these conditions are originated from inland location...